Equipment for continuously forming concrete barriers of the type commonly referred to as "Jersey" barriers is well known. Such equipment, also known as automated slip formers, includes a form or "mule" for defining the shape of the barrier, a hopper coupled to the mule through which concrete is delivered to the mule, and a drive assembly coupled to the mule and hopper for causing these elements to move along a path extending next to the surface on which the barrier is to be erected. An exemplary piece of such slip forming equipment is manufactured by Miller Formless Company, Inc., of McHenry, Ill., and is identified by model number M-8800.
Known slip forming equipment is well adapted to continuously form horizontally extending concrete traffic barriers having either smooth outer surfaces or outer surfaces having continuous, horizontally extending grooves, ridges, or other concave or convex surface texture. Unfortunately, known slip forming equipment is not adapted to form horizontally extending concrete barriers having vertically extending, transversely extending, or other nonhorizontally extending surface texturing. This limitation of known slip forming equipment is especially undesirable in areas where state or local construction codes require that one surface of concrete road barriers include nonhorizontally extending surface texture. For instance, construction codes in the state of Washington require that, under certain circumstances, the outer surface of concrete traffic barriers installed along the outer edges of bridges include vertically extending striations. At present, such bridge barriers are formed on a noncontinuous, section-by-section basis, at a cost far in excess of that for continuously forming horizontally extending concrete barriers of similar height and thickness.
Equipment is also known for vertically slip forming concrete abutments, silos, and other structures characterized by vertically extending concrete walls. Such equipment is disclosed, for instance, in U.S. Pat. No. 3,453,707 to Johansson, and U.S. Pat. No. 4,314,798 to Pettersson. The Pettersson apparatus includes a yoke and a pair of leg assemblies attached to and extending downwardly from the yoke. The leg assemblies are spaced a predetermined distance from one another, and the apparatus includes means for moving the leg assemblies toward and away from one another. In use, two form halves are positioned between and supported by the leg assemblies. Concrete is then poured between the form halves which are caused to move upwardly in a continuous manner by moving the yoke and leg assemblies upwardly. Although known apparatus for vertical slip forming may be satisfactorily employed in the fabrication of vertically extending walls, such apparatus are not adapted to form horizontally extending barriers, or vertically extending walls having other than vertically extending surface texturing.